Collaborative Research: Linking Permafrost Soil Inundation to Carbon and Mercury Uptake in Aquatic Food Webs of the Arctic

汞元素是人类活动释放的一种常见的全球污染物，对全世界的环境和人类健康都有影响。汞的一种形式是甲基汞，它是由微生物在一个称为汞甲基化的过程中产生的，可以在整个食物网的水生生物中积累到有毒水平。北极的永久冻土含有大量的古代汞，由于北极变暖，这些汞也从融化的土壤中释放到淡水和沿海海洋环境中。北极地区农村社区的妇女和儿童依靠捕鱼为生，最容易受到汞的毒性影响。围绕北极汞的核心问题是，从融化的永久冻土中释放出的古老汞与来自大气的新汞的相对重要性，以及北极景观中迅速变化的条件将如何影响这些不同汞来源的转化和食物网吸收。为了解决这些问题，本研究将使用多种方法来跟踪释放，转换和吸收的碳和汞从永久冻土到水生生态系统，随后到居民鱼。该项目的另一个目标是开发一种实用的方法，对湖泊和池塘中具有永久冻土的重要汞转化潜力进行建模。通过与阿拉斯加北极地区农村社区的对话，我们将与受汞污染严重影响的人们分享我们所了解的情况。我们还将帮助培训下一代研究这些问题的科学家。这项研究将利用阿拉斯加西北部美国国家公园管理局土地上一系列不断扩大的热喀斯特湖泊和最近形成的海狸池塘进行。首先，实地研究将针对微生物甲基化的永冻汞和它的依赖永冻碳使用宏基因组学，实地实验，碳呼吸途径的测量。接下来，将使用放射性和稳定同位素（碳，汞，氮和硫）和同位素混合分析的组合，定量水生食物网中的永冻层碳和汞的吸收。同位素混合模型旨在区分北极食物网中的古代与当代汞和碳。其目标是建立一个过程级的动员，微生物转化，从永冻土到水生食物网的碳和汞的生物吸收的理解。最后，实地观察将为湖泊和池塘的建模工作提供信息，以建立水体的热和生物地球化学制度与汞甲基化之间的联系。这种过程级科学与预测模型开发的结合将为了解北极系统在当前和未来条件下的汞循环提供必要的信息。研究结果将通过参加生存资源理事会会议传达给阿拉斯加北极地区的农村社区，通过与美国国家公园服务处的科学传播专家合作的公共演讲和媒体向公众传达，并通过会议研讨会和同行评审的期刊文章向科学界传达。本科生、研究生和博士后研究人员将与跨机构的合作者进行交叉培训并参与外展活动，以培养一支多元化且具有全球竞争力的STEM劳动力队伍，以应对该项目以外的未来环境挑战。该奖项反映了NSF的法定使命，并且通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The element mercury is a common global contaminant released from human activities that impact both environmental and human health worldwide. One form of mercury, methylmercury, is produced by microorganisms in a process called mercury methylation and can accumulate to toxic levels in aquatic organisms across the food web. Permafrost soils of the Arctic contain large stores of ancient mercury that are also being released to freshwater and coastal marine environments from thawing soils due to a warming Arctic. Women and children in rural communities in the Arctic that rely on subsistence fishing are most vulnerable to the toxic effects of mercury. The central questions surrounding mercury in the Arctic are the relative importance of ancient mercury released from thawing permafrost soils versus newer mercury from the atmosphere, and how rapidly changing conditions in Arctic landscapes will affect the transformations and food web uptake of these different sources of mercury. To address these questions, this study will use multiple approaches to track the releases, transformations, and uptake of both carbon and mercury from permafrost soils to aquatic ecosystems and subsequently to resident fish. The project further aims to develop a practical approach to model the potential for important mercury transformations in lakes and ponds with underlying permafrost soils. Through dialogue with rural communities in Arctic Alaska, we will share what we learn with people who are heavily impacted by mercury pollution. We will also help train the next generation of scientists working on these problems.The study will be carried out using a series of expanding thermokarst lakes and recently formed beaver ponds in U.S. National Park Service lands in northwest Alaska. First, field studies will target the microbial methylation of permafrost mercury and its dependence on permafrost carbon using metagenomics, field experimentation, and measurements of carbon respiration pathways. Next, the uptake of permafrost carbon and mercury in aquatic food webs will be quantified using a combination of radio and stable isotopes (carbon, mercury, nitrogen, and sulfur) and isotope mixing analyses. Isotope mixing models aim to differentiate ancient versus contemporary mercury and carbon in Arctic food webs. The goal is to establish a process-level understanding of the mobilization, microbial transformation, and biotic uptake of carbon and mercury from permafrost soils to aquatic food webs. Lastly, field observations will inform modeling efforts of lakes and ponds to establish linkages between thermal and biogeochemical regimes of water bodies and mercury methylation. This combination of process-level science and predictive model development will provide the necessary information to understand mercury cycling in Arctic systems under present and future conditions. The research findings will be communicated to rural communities in Arctic Alaska through participation in Subsistence Resource Council meetings, to the general public through public presentations and media in collaboration with a science communication specialist at the U.S. National Park Service, and to the scientific community through conference workshops and peer-reviewed journal articles. Undergraduate, graduate, and postdoctoral researchers will cross-train with collaborators across institutions and participate in outreach activities, to develop a diverse and globally competitive STEM workforce to address future environmental challenges beyond this project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.